9 - Renal Blood Flow, Nephron Physiology PPT Flashcards by Owen Bakewell

Where does unfiltered blood enter the kidney?

Renal artery

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Where does filtered blood leave the kidney?

Renal vein

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If renal blood flow (RBF) increases, what happens to the glomerular filtration rate (GFR)?

GFR increases

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If renal blood flow (RBF) decreases, what happens to the glomerular filtration rate (GFR)?

GFR decreases

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How is renal blood flow (RBF) regulated?

By increasing or decreasing arteriolar resistance

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What two hormones DECREASE renal blood flow by increasing arteriolar resistance?

Adrenaline (Epinephrine)
Angiotensin II

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What four hormones INCREASE renal blood flow (RBF) by decreasing arteriolar resistance?

Atrial Natriuretic Peptide (ANP)
Brain (Ventricular) Natriuretic Peptide (BNP or VNP)
Prostaglandin
Dopamine

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What are the two mechanisms of autoregulation of RBF?

Myogenic mechanism
Tubuloglomerular mechanism

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Describe myogenic mechanism.

When stretched by high blood pressure, smooth muscle cells in arterioles automatically contract

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Describe tubuloglomerular mechanism.

Macula densa releases adenosine which constricts the afferent arteriole when more sodium and chloride ions are detected in distal convoluted tubule.

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What’re the two parts of the nephron?

Renal corpuscle
Renal tubules

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What is the renal corpuscle made up of?

GLOMERULUS!

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What’s the dang glomerulus made up of?

Tuft of capillaries surrounded by a Bowman’s capsule, separated by Bowman’s space (this Bowman guy thinks he’s all that)

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How does blood reach the glomerulus? How does it leave?

Arrives via afferent arteriole, exits via efferent arteriole

Remember, Arrive Ugly & Exit Fresh (Afferent Unfiltered, Efferent Filtered)

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At the efferent arteriole, what does it divide into?

Peritubular capillaries that surround the renal tubule

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We touched on this briefly in the previous deck, but what is the glomerular filtration barrier?

A three-layered structure that separates blood within glomerular capillaries from fluid within the Bowman’s capsule.

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What are the three layers of the barrier and what is their purpose?

Endothelium
- made up of glomerular capillary endothelial cells
- features small pores that allow passage of solutes and some proteins but not RBCs
Basement membrane
- gel-like layer with tiny pores that block plasma protein passage due to negative charge and size
Epithelium
- made up of podocytes which wrap around the basement membrane
- blocks plasma protein passage

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GUARANTEED MIDTERM TEST QUESTIONS! What forces affect glomerular filtration?

Hydrostatic pressure (fluid) and oncotic pressure (protein), aka the 𝐧𝐞𝐭 𝐮𝐥𝐭𝐫𝐚𝐟𝐢𝐥𝐭𝐫𝐚𝐭𝐢𝐨𝐧 𝐩𝐫𝐞𝐬𝐬𝐮𝐫𝐞.

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What are the hydrostatic (HS) and oncotic (OC) pressure locations that affect filtration?

HS pressure of blood in glomerular capillary
HS pressure of filtrate in Bowman’s space
OC pressure of proteins in capillary

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Delving into the HS BP in the capillary, how does afferent arteriole vasoconstriction affect renal blood flow?

It 𝐫𝐞𝐝𝐮𝐜𝐞𝐬 𝐫𝐞𝐧𝐚𝐥 𝐛𝐥𝐨𝐨𝐝 𝐟𝐥𝐨𝐰, which 𝐫𝐞𝐝𝐮𝐜𝐞𝐬 𝐇𝐒 𝐁𝐏 𝐢𝐧 𝐭𝐡𝐞 𝐜𝐚𝐩𝐢𝐥𝐥𝐚𝐫𝐲. (GFR ⬇️)

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How does afferent arteriole vasodilation affect renal blood flow?

It 𝐢𝐧𝐜𝐫𝐞𝐚𝐬𝐞𝐬 𝐫𝐞𝐧𝐚𝐥 𝐛𝐥𝐨𝐨𝐝 𝐟𝐥𝐨𝐰, which 𝐢𝐧𝐜𝐫𝐞𝐚𝐬𝐞𝐬 𝐇𝐒 𝐁𝐏 𝐢𝐧 𝐭𝐡𝐞 𝐜𝐚𝐩𝐢𝐥𝐥𝐚𝐫𝐲. (GFR ⬆️)

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How does efferent arteriole vasoconstriction affect fluid in the glomerular capillary?

It 𝐢𝐧𝐜𝐫𝐞𝐚𝐬𝐞𝐬 𝐟𝐥𝐮𝐢𝐝 𝐢𝐧 𝐠𝐥𝐨𝐦𝐞𝐫𝐮𝐥𝐚𝐫 𝐜𝐚𝐩𝐢𝐥𝐥𝐚𝐫𝐲, which 𝐢𝐧𝐜𝐫𝐞𝐚𝐬𝐞𝐬 𝐇𝐒 𝐁𝐏 𝐢𝐧 𝐭𝐡𝐞 𝐜𝐚𝐩𝐢𝐥𝐥𝐚𝐫𝐲. (GFR ⬆️)

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How does efferent arteriole vasodilation affect fluid in the glomerular capillary?

It 𝐝𝐞𝐜𝐫𝐞𝐚𝐬𝐞𝐬 𝐟𝐥𝐮𝐢𝐝 𝐢𝐧 𝐠𝐥𝐨𝐦𝐞𝐫𝐮𝐥𝐚𝐫 𝐜𝐚𝐩𝐢𝐥𝐥𝐚𝐫𝐲, which 𝐫𝐞𝐝𝐮𝐜𝐞𝐬 𝐇𝐒 𝐁𝐏 𝐢𝐧 𝐭𝐡𝐞 𝐜𝐚𝐩𝐢𝐥𝐥𝐚𝐫𝐲. (GFR ⬇️)

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END GUARANTEED MIDTERM QUESTIONS. Continuing, how does urine flow blockage affect the HS filtrate pressure in Bowman’s space?

It 𝐢𝐧𝐜𝐫𝐞𝐚𝐬𝐞𝐬 𝐇𝐒 𝐟𝐢𝐥𝐭𝐫𝐚𝐭𝐞 𝐩𝐫𝐞𝐬𝐬𝐮𝐫𝐞 𝐢𝐧 𝐁𝐨𝐰𝐦𝐚𝐧’𝐬 𝐬𝐩𝐚𝐜𝐞 but 𝐧𝐨𝐭𝐚𝐛𝐥𝐲 𝐫𝐞𝐝𝐮𝐜𝐞𝐬 𝐆𝐅𝐑 (inverse relationship). (GFR ⬇️)

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An increase in plasma protein concentration can __________ OC protein pressure in the capillary (but GFR ⬇️).

INCREASE

A decrease in plasma protein concentration can __________ OC protein pressure in the capillary (but GFR ⬆️).

DECREASE

What is GFR based on?

The ultrafiltration pressure and capillary permeability.

What's reabsorption?

Retention of substances by moving them from the tubule to the arterioles

What's absorption?

Moving from the tubule to the blood

When does ONLY filtration occur (NO REABSORPTION)?

When dealing with products of metabolism like urea or creatine, and foreign substances such as drugs

When does filtration with partial reabsorption occur?

When dealing with electrolytes such as sodium or bicarbonate which are easily reabsorbed, and potentially secreted

When does filtration with complete reabsorption occur?

When dealing with nutritional substances such as glucose and amino acids

What is a secretion?

Any substance not reabsorbed such as organic acids, which are secreted into tubular fluid to become urine. They move from the arterioles to the tubules.

Can filtration remove all substances?

NO, but secretion helps to remove almost everything

List four facts about the proximal convoluted tubule!

1. It's the first renal tube segment 2. It receives filtrate from the renal corpuscle 3. It passes filtrate to the loop of Henle 4. It's lined by brush border cells

Which structure does the apical surface face and what is it lined with?

Faces the lumen and is lined by microvilli for absorption

What structure does the basolateral surface face?

Faces the interstitium

What is the prox. convoluted tubule surrounded by that reabsorb/secrete solutes from the blood?

The peritubular capillaries

What ions does the prox. convoluted tubule reabsorb into the blood?

- Na+ - K+ - Ca2+ - Cl- - Mg2+

Which ion is most important for reabsorption of water and solutes?

SODIUM (Na+)

Around ____ of the sodium that gets filtered into the tubular fluid is reabsorbed in the prox. convoluted tubule, and the remaining ____ goes on to the rest of the nephron.

1. 67% 2. 33%

The tubular fluid has about the same composition as the plasma, so it contains more or less sodium than the tubule cells?

MORE sodium

Tubular fluid flows down its concentration gradient and into tubule cells by various channels. What are these channels?

1. Uniport 2. Symport 3. Antiport

Symports and antiports are cotransporters, but what does that mean?

They can move two or more different solutes at a time

The sodium-glucose cotransporter moves sodium in the direction of its _________________ and uses that energy to move glucose into the cell or against its __________________, meaning there's a higher concentration of glucose already in the cell than the lumen.

𝓬𝓸𝓷𝓬𝓮𝓷𝓽𝓻𝓪𝓽𝓲𝓸𝓷 𝓰𝓻𝓪𝓭𝓲𝓮𝓷𝓽

Once the glucose enters, it quickly leaves the tubule cell via two channels called...

... GLUT1 and GLUT2

Where are GLUT1 and GLUT2 located?

On the basolateral surface

Is this movement of glucose passive or active?

PASSIVE- it doesn't require energy because the glucose concentration in the interstitium and blood is pretty low

Where do almost all the filtered glucose, lactate, AAs, phosphate and citrate get reabsorbed into?

The prox. convoluted tubule with the help of sodium

How is sodium pumped out through the basolateral side and into the intersitium?

By a solute pump called the sodium/potassium ATPase!

What's the transfer rate of the sodium/potassium ATPase (as in, the ratio of sodium to potassium)?

3 Na+ ions out, 2 K+ ions in (3/2)

Why does the sodium/potassium ATPase pump require its ATP?

Because it's pumping both Na+ and K+ against their respective gradients.

What keeps the intracellular Na+ level low?

The sodium/potassium ATPase pump

What's the result of a low intracellular Na+ level?

It allows Na+ to flow into the tubule down its concentration gradient on the apical surface.

What happens when Na+ ions get into the interstitium?

They diffuse into the capillary down its concentration gradient.

What's the preferred pH level?

7.4 pH

What cotransporter aids in bicarbonate reabsorption?

The Na+/H+ exchanger

There's an important buffer system in the prox. convoluted tubule that deals with carbonic acid. What enzyme splits the carbonic acid into water and CO2?

Carbonic anhydrase type 4 Wreck-It-Ralph is the CAT4 because he WRECKS stuff, pretty smart huh

Which enzyme facilitates the reverse reaction- making carbonic acid?

Carbonic anhydrase type 2 Fix-It-Felix is the CAT2 because he FIXES (or makes) stuff, someone give me an award

How much of the filtered bicarbonate is reabsorbed in the prox. convoluted tubule?

85%

How is roughly 50% of filtered urea reabsorbed?

Through diffusion across the cell, down its concentration gradient, and into the capillaries.

Is NH4+ (aka ammonium) secreted or reabsorbed?

Secreted, it is toxic!

On to the loooooop of Henle, where does the loop of Henle receive filtrate from?

The prox. convoluted tubule

Where does the loop of Henle send the filtrate to?

The distal convoluted tubule

(TRUE/FALSE): The loop of Henle establishes the osmotic gradient and allows for varying urine conditions.

(TRUE)

What is the vasa recta?

Peritubular capillaries that follow the loop of Henle

What's the osmolarity of tubular fluid leaving the prox. tubule?

300 mOsm/L, same as the interstitial fluid around the tubule

What are the 6 contents of the tubular fluid?

- Water - Sodium - Potassium - Chloride - Calcium - Urea

What does the osmolarity of the medullary interstitium become as it reaches the bottom of the loop?

1200 mOsm/L

What is the thin descending portion of the loop of Henle solely permeable to?

WATER

What is the thick ascending portion of the loop of Henle permeable to?

- Sodium - Magnesium - Chloride - Calcium - Bicarbonate - Potassium

What can enter the thick ascending portion of the loop of Henle?

Hydrogen

What lines the thin descending portion of the loop to allow only water to pass through?

Aquaporin proteins

Why don't solutes leave the tubular fluid in large quantities?

There's just very few channels for them to exit through, this is by design. It's to keep them concentrated while removing the wata

The thin ascending limb is ____________ to water.

Impermeable

What channels does the thin ascending limb have in abundance?

Sodium and chloride channels

As the tubular fluid travels up the thin ascending limb, what osmolarity will it reach at the top of the thin ascending limb?

600 mOsm/L

What makes the thick ascending limb thicc?

Being made up of cuboidal epithelium instead of squamous cells.

Cuboidal cells don't contain aquaporin, so what does this mean for the thick ascending limb?

It is IMPERMEABLE to WATER!

What will the osmolarity be at the top of the thick ascending limb and why?

325 mOsm/L because solutes continue to move out of that splendid tubular fluid

What is the process of creating this osmolarity gradient called? No, not Bob.

Countercurrent multiplication

How does countercurrent multiplication work?

It uses ATP to build up the concentration gradient and reabsorb water into the interstitial fluid via passive diffusion.

How is the distal convoluted tubule (DCT) different from the proximal convoluted tubule?

The DCT is more hormonally controlled therefore more precise and accurate

Where does the DCT receive filtrate from?

The loop of Henle

Where does the DCT send filtrate?

The collecting duct

The DCT is composed of ________ and _________ portions

1. Early 2. Late

What is the DCT lined with?

Brush border cells

The early portion of the DCT is ____________ to water

IMPERMEABLE

What is the early portion of the DCT permeable to?

- Na+ - Cl- - Ca2+ - Mg2+

What's the late portion of the DCT permeable to?

- Na+ - Cl- - ADH - H2O - HCO3- - K+

What can enter the late DCT?

H+ and K+

There is a Na+/Cl- cotransporter present on the apical surface of the early DCT. What does it function to do?

It moves 1 sodium and 1 chloride ion into the cell! Sodium will be moved along its gradient, and chloride will be moved against its gradient. Chloride will then leave through the Cl- channels on the basolateral side and go down its gradient.

Similarly to the Cl- channels on the basolateral surface, there are ____ channels on the apical surface of the DCT alongside _______ channels on the basolateral surface of the tubule cells.

1. Ca2+ 2. Na+/Ca2+

Calcium reabsorption is regulated by what hormone that is secreted by the parathyroid glands?

Parathyroid hormone

What's the effect of parathyroid hormone binding to tubule cells?

Reabsorption of calcium increases

In the late DCT and collecting duct, what cells are dispersed among the tubule cells?

Principal and alpha-intercalated cells

How do alpha-intercalated cells remove H+ ions?

They pump them across the apical surface and into the lumen of the nephron.

What is the medullary collecting duct permeable to?

- Na+ - Cl- - ADH - H2O - Urea - HCO3-

What can enter the medullary collecting duct?

H+ ions

Within the DCT, there is a net movement of _________ and __________ into the blood, while H+ is pushed into the tubule.

1. Sodium 2. Chloride

What hormone regulates the DCT and collecting duct?

Aldosterone, which is made in the adrenal cortex

What does aldosterone trigger after diffusing across the membrane of principal cells?

It triggers the increased synthesis of the ATP-dependent potassium pump and Na+/K+ ATPase transporter.

What do the two aldosterone-triggered pumps accomplish?

They increase Na+ absorption and K+ secretion.

Refresh: What does parathyroid hormone seek to help absorb?

Calcium

Refresh: When the body wants to retain water, what does the pituitary gland secrete?

ADH

ADH binds to principal cells via a _________ receptor, then triggers the vesicles contain aquaporin 2 to bind to the basolateral and apical membranes.

protein

What does ADH's activation of the aquaporin 2 vesicles accomplish?

It allows water to rapidly cross the apical membrane and get into the cell, then continue across the basolateral membrane into the interstitium and nearby peritubular capillaries.

This process of osmosis shifts water from the _________ back into ___________.

1. Lumen 2. Circulation LAST CARD GOOD JOB!! It is currently 1:08am Aug 20, 2024

9 - Renal Blood Flow, Nephron Physiology PPT Flashcards

(108 cards)